Contents

Overview

Introduction

The Combine is a vast empire spanning multiple dimensions. The empire is inhabited by an unknown number of sentient, intelligent species, and appears to be governed by a race of bizarre, artificially-evolved Advisors (see below). The Combine expands its empire by invading worlds and enslaving the dominant species to be exploited as it sees fit. By manipulating these inhabitants, through methods including bioengineering and implantation, the Combine creates a race of super-soldiers uniquely adapted for the environment of that particular world. This process results in a highly mobile and adaptive military force which is able to respond to any threat and crush any opposition. The reasons behind the Combine's imperialism remain unknown throughout the game.

Note that the name "Combine" is not the actual name of the alien race or their empire; rather, it is the name by which humans refer to both. It is also worth noting that vocal stress is placed on the first syllable. The name is pronounced as the nounCOM-bine, as in combine harvester, as opposed to the verb form com-BINE, as in "to join together or unite." The actual name of the Empire is never fully revealed: Dr. Breen refers to it as the Universal Union, but it is unknown if this is the official name used by the Empire itself.

Until recently, many players speculated that the Combine may have possibly controlled Xen. However, new information [1] (discussed here [2]), from Half-Life's creators reveals the truth. The Combine Empire was engaged in a war with the Nihilanth's race, and, through means unknown, managed to force them out of their original homeland. The Nihilanth's race was then forced to seek refuge in Xen. The Combine could not follow them to Xen, as the Nihilanth was keeping the portal closed. However, scientists at the Black Mesa Research Facility on Earth accidentally opened a portal between Earth and Xen. After Gordon Freeman killed the Nihilanth, the portal opened, allowing the Combine to teleport its forces into Xen. Once there, the Combine became aware of the portal storm opening a gateway to Earth, and summarily used their forces stationed on Xen to invade and conquer Earth.

Earth is one of the Combine's most recent annexations, acquired following Earth's surrender at the end of the Seven Hour War. Following the standard Combine process, members of Earth's dominant species have been modified to form a new arm of the Combine military. Whilst these soldiers are primarily used as a permanent Combine garrison on Earth, in-game dialogue suggests that units of the Transhuman Overwatch are used across the Combine Empire.

Combine Advisors

The Advisor's grub-like appearance was inspired by the works of science fiction author Frank Herbert.

The Combine Advisors are the face of the Combine Empire, suggesting that they are probably the original master race behind the alien empire. They briefly appear in the game, in Doctor Breen's office, on giant monitors. Physically, they resemble large grub-like creatures, belonging to a species which most likely passed its singularity long ago. As a result of their expertise in developing advanced technology, the Advisors have evolved to an artificial state which is undoubtedly vastly different to their original physical state. They seem to be unable to manipulate objects or move around on their own, they are virtually blind, and they have a large number of other physical handicaps. As a result, the Advisors are totally dependent on their highly advanced technology in order to survive, and are probably unable to live without their mechanical aids. However, because of their life support, they have reached a technical immortality.

In terms of size, Advisors are about as large as a rhinoceros. They move using a form of advanced hover technology, possibly the large blue glowing devices on their backs. Despite their obvious intelligence and technological expertise, the Advisors are virtually featureless, with no visible eyes, ears, mouth, or limbs, explaining their many mechanical augmentations. As their natural eyesight is so poor, they rely on a vision enhancement device, and in order to help them breathe, their faces are covered by what appear to be respirators, from which a hose leads to a tank. Advisors rest inside a metal cradle which has two mechanical claw-like arms protruding from the upper section. Each Advisor wears a stitched olive-green body suit, leaving only the mostly featureless face and part of their tail fully visible. The suit also has a black collar adorned with golden hieroglyphics on it, possibly the original race's form of writing. There is similarity in both the colour and texture of the Advisor's body to that of the Nihilanth, the original game's final boss. This may or may not have been intended.

Despite their crippled physical state, the Advisors have become highly evolved mentally, and are capable of telepathy and telekinesis. Slashing animations revealed by the Half-Life 2 Model Viewer suggest that the player may have been intended to fight one of these creatures, most likely as a final boss.

Combine teleportation

Despite the advanced level of the Combine race, it seems to be lacking skill in teleportation. Dr. Mossman explains that the Combine can only teleport from one universe to another, but not to different locations in the same universe. The teleportation method used by Dr. Kleiner and Dr. Eli Vance can do this, though, which is why the Combine wants the technology. Dr. Mossman was actually helping the Combine build a teleporter capable of doing this, in Nova Prospekt, but, however, as Nova Prospekt was destroyed during Alyx and Gordon's escape, it is most likely that the Combine actually gained nothing in the end.

The Combine's method of teleportation, as limited as it is, still requires a large amount of power and huge machinery to perform, as seen at the end of the game, where Doctor Breen was attempting to escape from the Citadel using a Combine teleporter. This teleporter required an entire reactor, called the "dark fusion reactor," to power it, while the teleporters used by Dr. Kleiner and Dr. Eli Vance require only small amounts of power, and very little machinery. The reason for this is because they use Xen as a "dimensional slingshot," while the Combine doesn't, instead teleporting directly from one universe to another.

Invasion of Earth

Newspaper clippings found in Eli's Lab in Black Mesa East depict scenes from the Seven Hour War.

Following the Nihilanth's demise, the Combine was able to use the portal storm that was occurring at the time to continue on to Earth, where it launched a massive invasion that culminated in the Seven Hour War. Statements made by the G-Man suggest that the human race was unable to mount any effective resistance to the Combine armies, and that Earth's military forces were almost instantly overwhelmed. Former administrator of the Black Mesa Research Facility, Dr. Wallace Breen, negotiated a surrender on Earth's behalf and was therefore appointed the administrator of the Combine's forces on Earth - the Overwatch.

Half-Life: Alyx, which takes place between the events of Half-Life and Half-Life 2, focuses on Alyx Vance and her father Eli as they fight the Combine's occupation of Earth.[2]

Combine dominance on Earth

The Combine rules Earth from a giant tower in City 17, called the Citadel. According to unused scripts and backstory by Valve, there may be a Citadel in every city, although this has been disputed as existing in the official game story. At the end of the game, as Doctor Breen attempts to teleport off of Earth using the dark fusion reactor, a massive portal is created and several buildings that resemble Citadels are visible.

At the start of the game, the Combine has almost complete dominance of Earth, and has no idea who Gordon Freeman is. However, Doctor Breen immediately informs a Combine Advisor of Gordon Freeman during the teleport accident, in which Gordon Freeman appeared in Doctor Breen's office for a brief amount of time. Only a few handfuls of rebels, loosely organized in a ragtag resistance, are secretly opposing the Combine. Gordon Freeman's actions after his return eventually inspire a massive insurrection against the Combine, which results in a full-scale street war between the citizens and the Combine forces.

The original Combine race do not seem to have a presence on Earth at any point in the game. The reasons behind the Combine's desire to control the Earth are unknown, other than the absorption of Earth's resources, and the enslavement and exploit of its dominant species - the humans.

Suppression field

The Combine, since gaining dominance on Earth, has imposed something known as a suppression field. The suppression field acts to eliminate fertilization in humans thus bringing the human birth rate to a halt. Doctor Breen addresses this issue to the people via a broadcast during the early levels of Half-Life 2, as the response to a letter written to him by a "concerned citizen," and claims that the field will be deactivated once the humans prove they no longer need it. During the game, resistance members occasionally make humourous remarks such as: "When this is all over, I'm gonna mate," about the suppression field.

How the suppression field functions is currently unknown, and no other information about it is revealed during the game, except the fact that it exists. It is currently unknown whether the Combine imposes a suppression field on other races they conquer.

Mind control

Comments at the train station at the start of the game suggest that the Combine have been drugging (if not outright poisoning) the populace through their water supply. One frantic citizen says "don't drink the water...they put something in it, to make you forget." This is not mentioned outside this one piece of dialogue.

Human genocide

Some players theorise that all remaining children have been killed by the Combine. Evidence such as the ghostly laughs of children that can be heard in the playground outside one of the apartments in the first level, the crying couple that can be seen shortly thereafter, the fact that the player doesn't see any children in the most human-populated areas, remarks by resistance members such as "I'm glad there's no kids around to see this," and the presence of deserted toys such as baby dolls supports those theories.

Of course, there is the possibility that this could have been a design issue; a game where children could be shot could have become a contentious issue in the media. Just as there are no children in the game there are no babies and adolescents present either.

A more likely explanation is that the Combine placed the suppression field immediately following their victory over Earth's forces, and given that the Combine have been occupying Earth for at least ten years and possibly longer, the humans that Gordon sees throughout the game are possibly the last humans born naturally. According to commentary from Viktor Antonov and Dhabih Eng in Half-Life 2: Raising The Bar, a setpiece for Gordon's journey was a factory run by child labor and child citizens had been designed, but it became apparent to the design team that the Combine had suppressed human reproductive cycles for many years.

Depletion of Earth's resources

It is evident at several points in the game that the Combine are depleting Earth's natural resources. One of the official Half-Life 2 descriptions details how Gordon Freeman must return to "an Earth infested with aliens and being picked to the bone." One of the most noticeable signs is that Earth's ocean levels have dropped dramatically. This can be seen during the coastal chapters Highway 17 and Sandtraps, and the waterways of City 17 in Route Kanal. The coastline is littered with boats and ships resting on what was previously the seabed, and there are various docks and piers which are no longer standing in water, but instead jut out of the old seabed. At the beginning of Highway 17, Gordon arrives at a harbour which is now a considerable distance from the water's edge. Indications of the previous sea level can be judged by moss which had previously gathered on harbour structures at the edge of the water, but which now lie several metres higher than the ground level.

The huge digging mechanisms at the base of the Citadel are another example of how the Combine are depleting Earth's resources. The huge machines continuously pound the ground at the base of the Citadel, creating a huge chasm as they deplete the natural resources. Although not a "natural resource," City 17 itself is being devoured, as Combine walls spread outward from the Citadel, consuming the city's buildings. It is unknown whether the Combine are purely using this method to destroy the city, or whether they're actually gathering raw materials from the city's structures.

During the development of the game, the Combine originally had a huge industrial facility which was referred to as the "Air Exchange," which gradually absorbed Earth's air and replaced it with chemicals and other substances which were harmful to humans, but most likely ideal for an environment that the Combine master race could inhabit. It was up to Gordon Freeman to travel to the Combine Air Exchange via a ship called The Borealis, which was captained by a man name Odell. Gordon's actions at the Air Exchange were to trigger the human insurrection against the Combine in City 17, but as the level was dropped, this was instead made to happen due to Gordon's actions at Nova Prospekt. The Air Exchange concept was dropped during development, and it's uncertain whether or not it exists in the official storyline of the game, but as there are no in-game references to it, it is likely that it, in fact, does not exist.

Humanoid Combine

The primary military force of the Combine on Earth is the humanoid Combine Overwatch (referred to by Doctor Breen as the "Transhuman arm of the Combine Overwatch"): humans who have been modified into "trans-human" cyborgs. They are the most frequently-encountered foes throughout Half-Life 2.

Civil Protection, referred to in brief as CPs, and also commonly known as Metro Cops, police inner-city areas and keep citizens in line through the use of intimidation and physical force - ranging from random beatings, questioning and "inspections," to outright murder. They also patrol the canals outside of the city for escapees. Based on quotes heard during the game, Civil Protection appear to be nothing more than humans that willingly join the Combine for privileges and better life standards, such as adequate food. Unlike Overwatch Soldiers, they do not appear to be modified or enhanced in any way, although they wear respirators.

Certain radio transmissions heard over the Civil Protection's radios suggest that they get rewarded with sex simulations (normal citizens can not have sexual intercourse due to the Combine's suppression field). Other radio transmissions suggest that additional privileges are gained if the personnel have their memory replaced. It is possible that the Civil Protection personnel work their way up the ranks by having more and more human features and characteristics erased.

In the first few chapters of the game, the Civil Protection are armed with H&K USP Match pistols and stun batons. However, later, they will occasionally carry H&K MP7 sub-machine guns. It is seen by some gamers as an amusing jab at Heckler & Koch since they primarily sell to government entities only.

Some cops are also outfitted with deployable manhacks, which they will release at opportune moments, while other cops have the ability to call in reinforcements by launching flares (typically from Combine watchtowers).

The tactics that the Civil Protection employ are basically strafing to avoid enemy fire or hiding behind cover when they are wounded. When a Metro Cop is killed, its radio emits a prolonged tone (reminiscent of the sound of a "flat-lining" EKG), and any other cops nearby will usually start chattering on their radios. The presence of Civil Protection forces can usually be detected by telltale radio chatter in quiet areas. Civil Protection officers are typically talked to by a female voice over their radios (voiced by Ellen McLane), resembling a dispatcher. She will inform them of mission objectives, reward reminders, downed units, and a variety of other information to keep the officers informed and up-to-date.

Civil Protection are generally kept separate from Combine military units, such as Overwatch Soldiers or Synths, and stay in a policing role within the cities. They travel in APCs and dropships, and are often accompanied by scanners or manhacks.

Take note that Resistance members wear vests salvaged from Civil Protection officers as protection.

Overwatch soldiers, also known as Combine soldiers are intelligent infantrymen that work well in a team and use a variety of attack methods. While Civil Protection has jurisdiction over the relatively minor affairs of policing the city, Overwatch soldiers can be found everywhere, and form the backbone of the Combine military occupation force. In this role, they are also the most versatile units the Combine have at hand.

Combine soldiers will commonly travel using dropships or APCs. They are typically armed with either an H&K MP7 sub-machine gun, Franchi SPAS-12 shotgun, or an Overwatch Standard Issue Pulse Rifle, and usually carry a supply of grenades. Certain soldiers will use Overwatch sniper rifles, although they are less common (see below). Combine soldiers also serve as the pilots and gunners of the Combine's hunter-choppers.

An Overwatch soldier with items of clothing removed, revealing the modified human. Take note that this screenshot was taken using the Half-Life 2 Model Viewer but the soldier can also be seen in-game on a monitor in Nova Prospekt.

Combine soldiers are initially found mostly in the coastal wasteland outside the city, patrolling the highways for resistance activity and staffing Combine outposts. They can, however, be found anywhere the Combine requires direct military action, as soldiers can be transported from the Citadel to a desired area via dropships. Overwatch soldiers are also tasked with guarding very high-security areas, monitoring stalkers in the Citadel and serving as staff in Nova Prospekt.

Nova Prospekt's guards wear special blue-and-yellow uniforms, but are otherwise identical to their grey-and-white counterparts. Also, standard soldiers have blue goggles, while their Nova Prospekt counterparts have yellow ones. New types of Combine soldiers, which wear olive-green uniforms with orange goggles, can be seen in some Half-Life 2: Aftermath screenshots. Their specific role is currently unknown, but some players have theorised that they may be specially-trained reinforcements or containment units. Interestingly, the new "Aftermath soldiers" appear on the Half-Life 2: Deathmatch background screen. On a related note, Valve stated that certain Aftermath content will make it into Deathmatch; the new Combine soldiers are most likely to become a new player model.

Combine soldiers are confirmed to be humans that have undergone extensive modifications including, but not limited to, brain surgery, chest surgery and implantation of various mechanical devices in the throat and around the abdomen, and are likely to have their memories replaced. This procedure is carried out at Nova Prospekt. Some players like to think of Combine soldiers as a human version of the Synth.

Despite the extensive surgery and modifications they receive, Overwatch Soldiers still appear to have certain human characteristics - for instance, they will grunt in pain when attacked, and during the Nova Prospekt chapter, Doctor Breen is giving what appears to be a morale-boosting speech to them, indicating that they still have human emotions to a certain extent. They also communicate over radios, but unlike Civil Protection officers, are not spoken to by dispatchers. Based on announcements made over the public address system of Nova Prospekt, punishments for failing to achieve objectives include "permanent off-world assignment". The threat of being reassigned to what may be the fringes of the Combine empire is apparently an effective method of motivating soldiers to succeed.

The following combat tactics are true for both Combine Soldiers and Combine Elites:

Soldiers usually stay behind cover and only come out for a short time to fire.

They frequently attempt outflanking maneuvers to surround enemies.

When faced with an enemy that is too close to safely fire upon, they will use the butt of their weapons to strike the enemy and attempt to drive him or her back.

Overwatch sniper

Overwatch snipers are highly trained soldiers, who hide themselves in high, concealed locations that offer a good field of view. The only way to detect a sniper is by the blue sighting beam and the distinctive crack of his sniper rifle. Typically, these snipers are so well-entrenched that they can only be killed with a well-thrown grenade or other explosive device. The explosion will typically blow the sniper out of his hiding spot, but his weapon never seems to fall to the ground for the player to collect.

Combine snipers also seem to take the doctrine of "Shoot anything that moves" quite literally; aside from their fellow Combine, they will fire upon anything that moves, including crows, headcrabs, pigeons and zombies. Combine snipers can be seen shooting any breakable items around a hiding target, in order to eliminate the amount of additional cover that the target can use.

It is likely that the player was intended to use a Combine sniper rifle during the game, but that the concept was dropped during the development of Half-Life 2, in place for the resistance-built crossbow.

Early concept art of the snipers reveals that they might have been female at some point, much like the human Black Ops assassins from Half-Life. This version wore a similar stark-white outfit worn by Combine Elites, but was much less bulky to allow the sniper to move around easier, and make less noise which might alert the target to its presence. Another concept that was not utilized was the idea of the sniper being a much more robot-like combat synth with three eyes.

Sporting a distinctive white uniform with a single red ocular lens, the Elites are the deadliest of the Combine Overwatch infantry, and are theorised to be altered even further than standard soldiers. They use similar combat tactics as regular Combine soldiers, save for a few improvements.

The Elite soldiers are tougher, have better accuracy with weapons, and inflict more overall damage than regular Soldiers do. They are always armed with an Overwatch Standard-Issue Pulse Rifle, and are the only units who seem to have access to the weapon's secondary-fire energy orb. They use this advantage without hesitation and with deadly accuracy. The orbs they fire, however, can be caught by Gordon Freeman's gravity gun, to be used as he sees fit. The orb, though, will explode after a certain amount of time, whether flying freely (it is not affected by gravity, and can bounce off anything it doesn't kill instantly) or if left in the gravity gun's field.

Elites typically fight in squads of their own kind, but will occasionally lead squads of regular soldiers. Elites are fewer in number than regular soldiers, and are thus reserved for the more critical combat missions, where deadly tactics are required. They also serve as Doctor Breen's personal guards.

Early conceptual work on the Combine Elite had emphasized their alien features: early Elite concepts had them as more ambulatory versions of the Combine Advisor, a Strider synth grafted down into the proportions of a human, and an asymmetrically proportioned cyborg synth, typically with a human face visible. The more conventional looking Elite, partly based off the concept for the unused female Combine Assassin, was chosen over the early concepts to avoid overshadowing the remarkable nature of the Citadel and to keep the Combine as a more elusive and transparent enemy.

Stalker

The product of extreme, brutal Combine engineering, stalkers are humans who have had their higher brain functions severed and their bodies physically altered. Their limbs have been removed and replaced with mechanical extensions; most organs, excess fat, as well as muscle have also been removed and what appear to be metallic augmentations added to parts of their body. Stalkers appear to be in constant pain, as their loud wheezing indicates. A stalker can't talk, and instead can only make beastly roars, most likely because its vocal cords, or perhaps entire larynx, has been removed, as the metallic hole in their throats suggests. The lack of higher mental functions would also prevent them from talking.

For ease of maintenance and to bring a physical dependence on the Combine, the stalker's digestive tract has been removed, resulting in the stalkers surviving solely on a saline solution that the Combine provides. Stalkers would originally have to work to gain the metallic legs, proving they could be trusted with additional movement. All stalkers appear to come from male human beings, as they have facial hair stubble.

Humans are turned into stalkers at Nova Prospekt, and are then transported to the Citadel to do slave labour for the Combine. They are transported by razor trains, and are confined in pods during the transportation. Despite being seen in Nova Prospekt and the Citadel, stalkers are never actually engaged in combat during the game.

It appears that the citizens of City 17 have a full knowledge and understanding about stalkers, what they are, and how and where they are "made"; as a citizen says, "They're never gonna make a stalker out of me!" Alyx also comments on Nova Prospekt: "It used to be a high-security prison, but it's something... much worse now." Barney also makes the comment, "He was about to board the express to Nova Prospekt!" at the start of the game. All comments indicate that the citizens know about stalkers, as well as Nova Prospekt.

Stalkers, when spawned using the console, shoot lasers from their feet at the player. This is unfinished code originally intended to be in Half-Life 2 - the laser was originally supposed to be fired from the tools attached to the stalker’s head. The laser might have also been intended to fire out of the small blue nodule on its chest. If the player kills a stalker the game will crash, as the model does not have a "ragdoll" state. Some mods have successfully avoided this problem.

On an additional note, stalkers were originally intended to be enemies, using fast leaping attacks in a similar way to the "Leaper" (Fast) zombies; they had little armor and were easily killed. The idea was dropped in the final version, most likely because the developers preferred only having zombies possess such startling abilities.

It has been confirmed that the stalkers will be making a more prominent appearance in the Half-Life 2 expansion, Half-Life 2: Aftermath, as enemies. Their new capabilities are currently unknown.

Combine synth

Synths are creatures that, over a course of imposed evolution and adaptation by the Combine, have come to fit a particular niche in the Combine military. Once self-replicating, organic, but robot-like creatures spread across different worlds, they were enslaved and assimilated into the Combine to become the backbone of their military.

Various types of Synth have been brought over to Earth by the Combine, but other types of Synth are likely to exist. The total number of different Synth is unknown. It is likely that Synths were the primary forces used by the Combine during the Seven Hour War, as the human-derived Combine units, as well as technology such as hunter-choppers and APCs, would have only started appearing after the Combine's rule on Earth had been established.

Entity: npc_combinegunship (only stays in one spot if spawned during play)

A powerful, autonomous aircraft that combines aspects of an airplane and a helicopter with Synth technology, the gunship is the Combine's most versatile combat aircraft. Gunships are used to attack enemies not normally accessible to ground forces, or in remote locations where air power would be more convenient. They are also sometimes used in a support role, called into specific trouble spots.

Gunships are powered by an array of different jet engines, visible on their belly, and a single, large, rotating insect-like wing at its rear that works similar to a helicopter rotor. Dragonfly-like compound eyes are positioned directly behind the gunship's pulse gun, and it is likely that they aim the weapon. The chassis itself has one large exposed compound eye on each side, which it might use to "see" or detect enemies under normal conditions. It should be noted that the aforementioned "dragonfly" eyes can be viewed in the Half-Life 2 Model Viewer as being able to extend downwards and sweep left and right, probably to maximize its chances of finding a target. Although lacking the hunter-chopper's explosive mines and intelligent pilots, the gunship surpasses the hunter-chopper in maneuverability and accuracy with its pulse gun.

Like most Combine Synths and vehicles, the gunship is invulnerable to light weapons and can only be damaged by explosives. Because of this weakness to explosives, gunships will give any incoming explosives, such as rockets, a priority over enemies, and will attempt to shoot them down. If there is more than one gunship, they will all attempt to shoot down an incoming explosive in order to protect each other.

Gunships are also equipped with a "belly cannon" which releases a matter disintegration blast, similar to that of the suppression device, directly beneath the gunship. This attack is never used during the singleplayer mission, but additional gunships spawned by players have been witnessed using such an attack.

Entity: npc_combinedropship (only stays in one spot if spawned during play)

Resembling a crab-like creature with ten limbs, the Dropship serves as the primary aerial transport unit of the Combine, they are used for any situation that requires fast air transport, mostly for attacks on remote locations. Dropships are also used as minelayers for deploying roller mines.

The front and two rearmost pairs of legs contain the engines that give the dropship lift and movement. The front two legs also hold retractable wings, used for maneuvering. The middle four legs are tipped with large gripping pads, and are used to carry various forms of cargo.

Dropships can transport most Combine forces, and they have been seen transporting Combine APCs, striders, roller mines as well as both Civil Protection and Overwatch soldiers in troop-carriers. Gordon Freeman's dune buggy is also stolen and carried away by a dropship after the battle at Lighthouse Point. The Overwatch soldiers and Civil Protection are transported in large, streamlined containers, equipped with a powerful, and highly-accurate mounted pulse gun.

Other than the troop-container's gun, the dropship has no weaponry, no means of attack, and is neutral to the player. It compensates for the fact that it has no attacks by being the most armored Combine unit. It is invulnerable to all forms of attack during the game. The cargo being held, however, is unshielded and open to damage. More often than not, though, the dropship's speed and the resilience of most cargo allow for a safe delivery before taking too much damage.

An extremely deadly and effective assault unit, the Strider is perhaps the most powerful, and the most feared of the Synths brought over to Earth.

Striders are essentially walking autonomous tanks, consisting of a beetle-like shell and three massive legs. The underside of the segmented shell holds the strider's external mechanics and two guns. The smaller of the two is a powerful and highly-accurate pulse gun, while the larger is a high-power "warp" cannon able to punch significant holes in the thickest concrete and vaporize enemies in a manner similar to the pulse rifle's orb, or suppression device fire. The firing of this weapon is signaled by a strange distortion of the light around the cannon's muzzle, a loud hum, and a smaller initial beam that indicates where the full force will hit. This process takes only a few seconds, leaving little time to react. Their powerful legs are also tipped with sharp spikes, which they use to impale weaker targets and kick debris.

Individual striders are used to patrol off-limit city streets and provide combat support for groups of soldiers. However, in major combat, striders are used in a role similar to manhacks on a city-wide scale, destroying possible shelters and flooding an area as a means of removing all enemies. Because of their greater effectiveness and value, they are used mostly in a defensive role. Striders fit this task well due to their destructive ability and remarkable maneuverability on even the harshest terrain. When unleashed, a strider can, and will, destroy an entire building in order to strike a handful of targets inside. Conveniently, their long legs can climb over any resulting debris or any barriers of up to several meters high. They can even crawl through very small traffic tunnels and parking garages, if need be, "digging" through barriers using their "warp" cannon.

Striders are also armored against all but the most powerful weapons, making non-explosive rounds useless against them. Luckily, striders tend to follow specific patrol routes when tasked with defending a limited area, making them easy to avoid, so long as shield scanners are not being used. When shield scanners do accompany a strider, they function as spotters for it, searching inside buildings and other places of concealment for targets the strider would otherwise be unable to see. Striders also work with Combine dropships, folding their legs into a compact shape that allows them to be transported.

Shield scanner

First Seen: Chapter Eleven, Anticitizen One

Health total: 30

Weapon damage: Dive (25)

Entity: Cannot be spawned during play.

The successor of the city scanner, the shield scanner appears for a brief time in later chapters of the game. It is very similar to the city scanner in terms of function and capabilities. The shield scanner features a stronger, and more blinding search light, and is equipped with a large pincer arm, which is kept concealed behind an armored hatch at its front, along with several additional sensors and parts.

The shield scanner, unlike the city scanner, has minor combat roles. A shield scanner uses its pincer arm to efficiently pick up and deploy hopper mines, giving it the additional combat support roles of a miniature equipment transport and minelayer. Shield scanners are also used as target-spotters for striders, alerting them to the presence of enemies hiding inside structures, or in other areas that might be used for concealment.

Crab synth

First Seen: Chapter Thirteen, Our Benefactors

Health total: N/A

Weapon damage: N/A

Entity: npc_crabsynth (has no AI)

This Synth is seen only being transported on a conveyor belt in the Citadel during Gordon Freeman's second pod-ride, and is never encountered in a combat situation. Its capabilities are unknown, but it appears to be a large ground-based combat unit with a weapon that resembles a minigun. No other information is available. Half-Life 2 storyline writer, Marc Laidlaw, hinted that the crab synth will be encountered in Half-Life 2: Aftermath.

Mortar synth

First Seen: Chapter Thirteen, Our Benefactors

Health total: N/A

Weapon damage: N/A

Entity: npc_mortarsynth (has no AI)

Like the crab synth, this creature is seen being transported on a conveyor belt in the Citadel during Gordon Freeman's second pod-ride, but is never encountered in a combat situation. Its capabilities are unknown, but it may be an airborne attack unit that launches solid, energy, or explosive projectiles, judging by its name and the catapult-like structure on its back. Half-Life 2 storyline writer, Marc Laidlaw, hinted that the mortar synth will be encountered in Half-Life 2: Aftermath.

Combine tech

The Combine, since gaining dominance on Earth, has invented a large number of devices and machines, some of which are offensive, and others which are used in the day-to-day policing and surveillance of the general populace. A majority of the Combine's technology present on Earth is actually nothing more than human technology re-interpreted and re-made by the Combine, using its own materials. Technology such as helicopters, turrets, and wheeled vehicles are all human technology, re-made by the Combine.

City scanner

First Seen: Chapter One, Point Insertion

Health total: 30

Weapon damage: Dive (25)

Entity: npc_cscanner

City scanners, often referred to simply as scanners, are piranha-like, flying security cameras used by the Combine to monitor City 17's citizens. They are equipped with a built-in camera and a blinding searchlight. City scanners have no weapons, but the blinding searchlight and the photographic flash emitted can temporarily stun a person. They are lightly armoured, and can easily be destroyed by launched objects, gunfire, or by simply being smashed with a hard object. When a city scanner receives critical damage, it attempts to crash itself into its attacker in hope of doing damage to them. They are powered by a single Combine battery, and a destroyed one will drop such a battery.

As the name implies, city scanners are used primarily in the city, rather than in out-of-city locations, such as the canals or the coast. It appears that city scanners are mass-produced in the Citadel, as they serve many purposes - including the obvious surveillance role, as well as reconnaissance, and the hunting of missing or wanted individuals. City scanners will typically accompany Civil Protection personnel. City scanners almost always work with other Combine units, but are typically not directly used in combat, and only have the role of informing other, more combat equipped Combine units about citizens and their locations, should there be need for combat. City scanners rarely travel alone, so the sight of a city scanner is usually an indication that there are other Combine forces nearby. In cases of emergency, city scanners can be mass-deployed in hundreds or thousands from the Citadel, to perform a city-wide, and possibly out of city search as well.

It also appears that a city scanner was used in one of the latest "evolutions" of Dog, the robot built by Eli Vance to protect his daughter, Alyx, while she was young, as both machines maintain a similar "facial" design.

Manhack

Manhacks are flying, gyroscope-like devices, slightly smaller than city scanners. They have three razor-sharp blades which constantly spin at extremely high speeds. The blades's spinning produces a high-pitched whine, which can be used as an indicator of a manhack's presence nearby. The manhack's blades are powerful enough to instantly slice through wood planks and fencing, but are unable to slice through stronger materials such as metal or concrete. Semi-intelligent, they have very little concept of self-preservation, careening off walls and through objects in the single-minded pursuit of their target.

Manhacks are deployed by the Combine (who call them "viscerators") and are used to scout areas too dangerous for city scanners. Manhacks never travel alone, but are usually deployed in groups of at least four or more. They appear to be fairly armoured against gunfire, and are more easily destroyed by being smashed with a hard object, which will cause it to become disoriented, and stop attacking for a couple of seconds as it re-stabilizes itself. The gravity gun is also very effective against them. Once in the gravity gun's field, they can be launched into walls, other hostile forces, or can be used as a chainsaw-like weapon.

Originally, a section of the game was designed where the Combine allowed citizens to, what seemed to them, play virtual reality games in something known as the "Manhack Arcade." The citizens playing these games had no idea that they were, in fact, controlling manhacks in real-life, and killing fellow citizens with them. The concept never made it into the final version of the game.

Rollermines are electrically-charged, spherical devices slightly larger than soccer balls that react to movement within a sizable radius. Rollermines are used as offensive and defensive traps by the Combine. As the name implies, they roll towards enemies in attempt to electrocute them. Extensively used along the coastal roads, the mines are deployed from the air by Combine dropships, in groups of two to four. Upon landing, the mines will remain inert or, if they land on softer terrain like soil or asphalt, they will burrow themselves into the ground, remaining almost invisible. When an enemy target is detected, the roller mine will pop out of hiding and roll towards it in a relatively straight line. They inflict damage to people via close-range electric shocks.

The mines can magnetically cling to a target vehicle and interfere with the steering, forcing the driver to either stop or drive off the road. Besides the damage inflicted by any resulting car wreck, attached rollermines pose little threat to the occupants of a vehicle, concentrating instead on shocking the vehicle itself. For this reason, rollermines are usually deployed in tandem with Combine soldiers, who would ambush the stranded individuals. Attached mines cannot be removed except through excessive force, and touching them will cause electrocution. They are also deployed in structures, taking any intruder by surprise. Rollermines can be destroyed with explosive devices, or alternatively may be picked up with the gravity gun and launched out of the way (or at enemies). Complete submersion in water also causes them to short-circuit and explode. Additionally, they can be eluded by being outrun, as they give up once a target is too far away.

Take note that Dog uses an inert rollermine as the ball during the game of fetch Gordon plays with him in the Black Mesa East scrapyard.

Hopper mine

Hopper mines are anti-personnel mines that hop into the air before exploding. These mines are carried and deployed by shield scanners. They are vaguely cone-shaped with three sharp "legs". When dropped, the mines use these legs to bounce around until they land right-ways up on a smooth surface. They then jam the legs into the ground, attaching themselves very firmly.

When an enemy target comes close, the mines light up and give off a warning chirp. If the enemy target gets too close, the mines will toss themselves unpredictably, nearly two meters (six feet) into the air, and explode upon contact with whatever they happen to hit on the way down, which is usually the ground. They also detonate if smashed too violently. Otherwise, they are impervious to nearly all forms of handheld weaponry, save for the gravity gun.

Because of their danger, immovability and extreme durability, hopper mines are impossible for most enemies to disable or defuse. Thus, they are used by the Combine almost exclusively to deter attacking enemy personnel, creating makeshift but often impassable barriers in seconds. They are used both indoors and outdoors, mostly in vital choke-points and occasionally concealed as traps.

Hopper mines use a friendly fire identification system which resets whenever they are picked up. The mines interpret a "friendly" unit as whichever faction placed it last. Thus, a mine placed by a citizen with a gravity gun will attack Combine, and a mine dropped by a shield scanner will attack citizens. This system is signaled through a color-coded light at the top of the device:

Green: The mine is armed and considers you to be a friend.

Red: The mine is armed and considers you to be an enemy.

Blue: The mine is neutral and has not yet armed itself.

No light: The mine has not yet been activated.

The ability to be turned against the Combine is most likely not an intentional feature of the mine or, instead, a reprogramming function built into the gravity gun, which was designed with mine removal in mind. In any case, the mines are unlikely to be placed by anything other than the Combine's shield scanners.

Sentry

Sentries are automated gun turrets mounted on a tripod. The Combine sentry shares a similar appearance and function with those used by the Hazardous Environment Combat Unit of the United States Marine Corps in the original Half-Life. However, the Combine version does not use secondary laser "tripwire" detectors, using motion detection sensors instead. The Combine sentry also has a narrower field of view and range of motion, whereas the HECU's turret is able to rotate and fire in nearly any direction.

The sentry's gun is loaded with the Combine's ubiquitous pulse ammunition, of which it has an essentially limitless supply. Sentry guns use a friendly fire detection system, allowing them to differentiate between Combine, alien and citizen. An individual gun's programming can be accessed and modified remotely through a separate computer terminal when necessary. Note that in Chapter 10, Entanglement, Alyx reprograms a number of sentry turrets, allowing Gordon to deploy them as defense against oncoming hordes of Overwatch soldiers.

The guns are often deployed as static defenses by the Combine, used to guard areas that are infrequently patrolled, or as a means to supplement a larger defense network. The turrets are fitted with small handles and are light enough to pick up and place by hand. When not in use, they are generally stored locked in small forcefield-equipped lockers. While the sentries appear to be indestructible, they are unable to target properly when knocked over. When this happens, they automatically fire in random directions for a couple of seconds, before shutting down until righted.

Against non-Combine enemies, assuming the sentry is still under Combine control, the gravity gun can be used to pick up the sentry from the rear, allowing direction of the firepower of the sentry gun to be in front of the player, shooting at any available enemies. However, using this tactic in the company of allies will cause them to be fired upon as well.

Combine turrets are placed in the floor, and unlike sentries, cannot be moved. Turrets will activate if their laser trigger is disturbed. They will spring up and begin firing at anything they consider to be hostile. Turrets have a 45-degree firing arc, which is indicated by two blue lasers emitted from the turret while it's activated. It is very easy to avoid turret-fire by simply staying out of the visible arc. While the turret is activated and idle, it emits a repetitive beeping sound, and if there are no hostile units in its vicinity, it will deactivate and retract back into the floor.

The turret, much like a sentry, is extremely tough and durable. The protective top of the turret, which resembles a large, metal tile, cannot be destroyed with any available weaponry. The only way to destroy a turret is by activating it, and then placing an explosive, such as a grenade, inside its pit, where its unprotected mechanisms lie. Once destroyed, the turret will retract back into the floor and its blue laser will deactivate.

Combine turrets can be found in the Overwatch Nexus, and are placed in areas containing equipment critical to the Combine, such as generators, or can be set up to guard hallways leading to such equipment, or other vital objects. They are usually placed in pairs, where they can cover each other with fire, or create crossfires for hostiles.

Special types of turrets exist which are only encountered in one room in the Overwatch Nexus. These turrets function in a similar manner to the standard turrets, except they have red lasers, and rather then being floor-mounted are attached to the ceiling. These turrets cannot be destroyed and feature a much more powerful pulse gun than the standard turrets which can tear anything to shreds within a matter of seconds. This, along with their close grouping, ensures almost certain death for anyone who activates them.

Although both types of turrets are only found in the Overwatch Nexus, it is likely that the Combine have installed such turrets in other structures and locations around City 17, which are not frequently patrolled by personnel, yet are important and require protection.

Mounted pulse gun

Mounted pulse guns can be found many places in Half-Life 2, including the canals, the wasteland, City 17, Nova Prospekt, etc. Soldiers on defensive structures dispatch mounted pulse guns to a nearby shield wall. Once in place, the gun can be fired by every humanoid entity (besides Vortigaunts, and zombies) with great intensity. Mounted pulse guns have unlimited ammo and have an attached flashlight, as well as a decorative laser. The mounted gun might be a reliable defense, but any explosive damage to the shield wall that the gun is mounted to will render the gun useless.

Ceiling mounted camera

Seen in many City 17 citizen checkpoints and the Citadel, ceiling mounted cameras are automated machines primarily used to identify individuals based on their appearance, using a built-in camera, and take appropriate action depending on the information gathered from the pictured individual. They have the ability to grant access to an entrance for valid citizens or Stalkers, or denying access to entrances for invalid citizens or unidentified individuals, which includes Gordon Freeman, while sounding an alarm and taking several photographs of the individual. Certain cameras may be seen programmed to redirect an invalid individual to an alternate access point or room, where they may be interrogated, or are directed to special destinations.

Ceiling mounted cameras are also seen assigned as detection devices, looking out for any intruders who may enter an area or room, and notifying Combine forces of the intrusion. Certain rooms under use by Combine units may also contain several ceiling mounted cameras for observation of units and security, and may be deactivated using a Combine command panel.

APC

Armoured personnel carriers are the main ground vehicle used by both the Combine's Civil Protection and Overwatch forces, for transport as well as for combat. Resembling large armored trucks or vans, Combine APCs are a good example of how Earth-based designs are often adopted by the Combine and re-interpreted with their alien technology.

The APC has a door on its right side as well as a set of double doors at its rear. The rear doors are likely for troops to enter through, while the front door is probably for the driver who possibly serves as the vehicle's gunner as well when not driving. The APC has unusual, striped tires which do not appear to be made out of rubber, and do not resemble any tyre-design on Earth. The hubcaps are made out of what resembles plates of metal arranged in a semicircle, leaving the rest of the wheel exposed.

The APC also features a very quiet engine even when going at high speeds, and is more than likely a four wheel drive vehicle. For a vehicle as large and as powerful as the APC, the differential and the driveshaft look undersized. Rather than this being the result of Combine technology, the true reason for this is likely to be nothing more than a way for the developers to save polygons, as those components are located under the vehicle and never really seen in-game. Another example of this could be the fact that the APC also lacks an exhaust pipe, but it is also possible that it uses a highly efficient, Combine-technology engine that doesn't produce exhaust and thus has no need for an exhaust system. The APC does seem to run on some sort of fuel, however, as there is something resembling a petrol (gas) tank cap on the left side of the vehicle.

The APC can carry a driver as well as four fully equipped soldiers and is armed with a mounted pulse gun and integrated missile launcher. The APC's biggest asset, however, is speed. Civil Protection officers use APCs as rapid response vehicles to reach conflict sites and crime scenes within minutes. Overwatch soldiers, on the other hand, use the vehicles mostly as fast and reliable transportation through the wastelands outside the metropolis. An APC can also be quickly carried over problematic terrain by a Combine dropship if required. When not in use, the APC can be hooked up as a power source for Combine devices such as force field pylons.

The APC has a siren which will typically be activated during a Civil Protection raid. It is never used by Overwatch personnel. Personnel inside the APCs can attack using the powerful short-range gun turret and volleys of longer-range, very accurate homing missiles. Luckily, enough gunfire can blow these missiles out of the sky or, at least, force them off course. APCs are sturdy enough that they are often used to simply smash into or run over the enemy. They are also very well shielded, offering complete protection from most conventional weapons.

The player does not get to drive a Combine APC during the game. The concept was dropped during development when playtesters complained that the APC was too slow compared to the other vehicles. This seems a strange complaint given the high speeds the APC seems capable of when driven by Combine forces during the game.

Hunter-Chopper

Incredibly powerful, the hunter-chopper is a combat helicopter used, as the name implies, for search-and-destroy missions against weaker targets. Like the APC, this vehicle is a conventional Earth design co-opted by the Combine and modified using its own technologies. It utilizes a two-man crew of Overwatch soldiers; one pilot and one gunner. The hunter-chopper is armed with a powerful pulse gun on a fixed mount and has the ability to drop explosive timed mines. The gun has a wide spread and is used mainly on slow or stationary targets. Before firing the hunter-chopper emits an audible "whining" sound that can be used as an indication of when the gun is charging up.

The spherical mines are used offensively - dropped directly in front of enemy vehicles and onto weaker structures. They detonate either upon contact with an enemy, or after a short timer counts down. The mines also float on water, allowing them to be used against boats and other water-craft. One hunter-chopper maneuver involves launching around fifty mines simultaneously during one high-speed bombard - effectively saturating an entire area. Hunter-choppers are among the fastest Combine units able to keep pace with, or outrun, almost any opponent. They are used mainly within the city and its outlying canals to search out and eliminate specific targets, especially those on foot. The hunter-choppers work both as lone attackers or as support units for other attack forces depending on the mission. At locations further from the city, however, such as the coast or locations where there is a large number of enemies, the Combine will typically choose to use gunships instead.

A group of City 17 escapees in the canals through unknown means managed to get hold of a hunter-chopper's pulse gun. When Gordon Freeman arrives at their camp, a Vortigaunt fits this gun onto his airboat. Gordon Freeman is then able to use it to take down the hunter-chopper that's been hunting him from the start of his mission.

Headcrab shells, also known as headcrab cannisters or headcrab rockets, are perhaps the most nefarious piece of technology the Combine possess. These shells rain down from the sky and release a payload of deadly headcrabs. Due to its use of living organisms in attacks, headcrab shells are classified as a form of biological weaponry.

Fired from a launcher only seen in the Lost Coast map, the headcrab shells are shot with a loud explosion and streak towards their target in a steady arc, leaving temporary vapor trails behind. These large projectiles can crash through most barriers, embedding themselves several feet even into concrete. At this point a hatch at the rear of the shell opens and reveals a metallic pipe-shaped container. Up to a half-dozen headcrabs climb from the end of this pipe and leap out into the crash site. Usually these are only basic headcrabs although fast headcrabs have been observed exiting a shell. Poison headcrabs are also used in shells, as seen in Lost Coast.

Once landed the headcrabs go about their usual practice of attempting to kill or enslave any human they encounter. The headcrabs will then simply infest the surrounding area, concealing themselves by burrowing into the nearby soil or taking up residence in pipes, vents, and other darkened hiding places. This infestation renders a significant area surrounding the crash site completely inhospitable to human life. While one shell is not a huge threat by itself, the effects can be horrific when the Combine shell an area with scores of these munitions. This happened to the mining town of Ravenholm prior to the events of Half-Life 2 which was inhabited by a large amount of escapees from City 17.

The Combine uses headcrab shells in much the same way as they use manhacks, only on a wider scale, being an efficient way to eliminate entire centers of Resistance. In addition to being used on their own as an effective weapon, individual headcrab shells are also used in a tactical role during some operations where they are used to weaken smaller targets, create disarray, and force enemies out of entrenched positions.

The suppression device, also referred to as the suppressor, is a stationary Combine weapon, which functions much like a large mortar except instead of firing shells it fires an extremely powerful and concentrated pulse. This slams into the ground, destroying objects, and disintegrating living beings within a 3-5 metre (9-15 foot) radius from the impact. The suppression device has to "warm up" before it can fire the pulse and the ground where the pulse will land begins to glow blue. This allows the the next target of the pulse fire to be predicted, and thus avoided.

The suppression device is powered by a series of Combine generators and possibly forms its ammunition from them as well. A suppression device was installed onto the roof of the "Overwatch Nexus" in City 17. During the game, Gordon, Barney, and a small band of Resistance fighters are required to disable all the generators in the building in order to power down the device in order that the Resistance on the streets can move more freely. The suppression device only appears once in the game but it is likely that the Combine may have installed similar devices in other parts of City 17 where there are large numbers of Resistance personnel.

It is unknown whether the suppression device functions on its own, or whether it has an operator, but the small interface and the binocular-like lenses suggest the latter, who is most likely a trained Overwatch soldier. No operator is seen during the game but it may be that he left the scene after the suppression device was disabled by the Resistance. Also, Combine personnel on the roof of the Overwatch Nexus suggest that they may have been guarding the operator, as well as the device itself.

The suppression device is not to be confused with the suppression field, which has a different function. The two are not linked to each other in any way.

Static and non-combat Combine property

A common trait of Combine structural engineering seems to be making most of their creations resemble imposing, fairly featureless monolithic constructs, save for the odd irregular patterns that dot their surface. On the other hand, some seem to be unnecessarily complex, while others exhibit properties that defy conventional physics.

The Citadel

The Citadel, ominously towering over City 17, as seen from City 17's canals

The Citadel is the giant structure from which the Combine governs the Earth. It is located in City 17, and resembles a massive, metallic and largely featureless skyscraper, rising some 3 kilometres (1.8 miles) into the sky, and possibly extending underground as well. The Citadel is heavily mechanised, and entire sections of it can move to allow for mass deployment of airborne Combine units such as Scanners or Hunter-Choppers. The Citadel appears to provide power to City 17, as power lines can be seen extending out of it. These power lines then join on to regular transmission towers and poles, to deliver power to the city.

As mentioned in the Raising the Bar book, entire blocks from City 17 vanished into thin air, as the Combine delivered the Citadel to Earth. There is a slight mention of this event in Doctor Breen's first speech in Half-Life 2, during which he states that the Citadel was "thoughtfully provided by Our Benefactors." The Citadel is embedded in a huge chasm, and is completely surrounded by enormous mobile walls which chew up material around the Citadel and prevent access from the streets. Attached to the base of the Citadel are other machines that pound the ground.

In the final chapters of the game, the player gets a first-hand look at the interior of the Citadel, which is amazingly different to its featureless exterior. Abundances of Combine technology are found within the Citadel, ranging from countless generators and force fields, to matter disintegration fields, to elevators and platforms that defy gravity, to giant tubes that transport unknown fluids. The architecture of the Combine has its greatest presence in the Citadel. The entire building is constructed from the same blackish blue metal which all Combine structures are made from.

There are railway systems in the Citadel that are used by Razor Trains to ship and deliver cargo. Large amounts of the cargo are new Stalkers from Nova Prospekt. The Stalkers are delivered in pods, and The Citadel includes a large transportation system for these pods. Tasks such as the operation of basic panels, or the repairing of damaged Combine equipment and units is done by Stalkers, under the constant supervision of Overwatch personnel or Scanners.

The Citadel is presumed to include large war factories, where Combine equipment, technology and weapons, as well as Synths are manufactured. Two types of Synth that were never encountered during the game, the Crab Synth and the Mortar Synth, can be seen being transported around on conveyor belts, indicating that they are manufactured in the Citadel.

On one of the very top levels of the Citadel is Doctor Breen's office, believed to be the location from which he transmits his Breencasts. Unlike the rest of the Citadel, Breen's office has a more classical, human look to it, although Combine architecture is still a very dominating feature in the room. The office includes various luxury items such as a wooden desk, mantle clock, leather seat, olden globe, as well as an expensive carpet. His office also contains a large set of monitors, from which he can communicate with contacts such as the Combine Advisor.

The very top of the Citadel contains the Combine's dark fusion reactor, which is used to power their tunnelling entanglement device, which is what they use to tunnel into Earth from their universe. At the end of Half-Life 2, Gordon Freeman manages to destroy the dark fusion reactor using orbs. This sends the Citadel into a critical state. The expected destruction of the Citadel, as Doctor Breen warned, will take out the whole of City 17, as well as everything else in the vicinity, and a mass flight from City 17, led by Gordon and Alyx, will have to take place. This is what the expansion pack, Half-Life 2: Aftermath is about.

Depot

The depot (as seen in Chapter 9, "Nova Prospekt") is an enormous structure towering over the Nova Prospekt prison facility. The depot is a nexus for Combine distribution of stalkers, as well as a storage center for political prisoners such as Dr. Eli Vance. The depot covers cellblocks D-E, and fills the area with Combine articles. In addition, the depot is a relay for the express train as seen in Chapter 1 ("Point Insertion") and again at the bridge in Chapter 7. Basically, once humans arrive at the depot they are held in sturdy metal straitjackets housed within metal pods. Once needed, the pods can be brought in at any point from within an access point. Just like the citadel, the depot has its own pod distribution center. Finally, the depot houses the Combine entanglement device, which in the end of Chapter 10 explodes because of overloading. It is believed that the explosion of the depot destroys all of Nova Prospekt.

Command panels

Combine command panels are found throughout City 17, Nova Prospekt, and the Citadel, and have multiple purposes. The command panels found in City 17 are generally used to open and close gates, and they may also be used for communication, as seen when Barney communicated with Dr. Kleiner in the opening levels in the game. The majority of command panels found in Nova Prospekt are used to work the systems around the facility - such as gaining access to surveillance cameras or transporting prisoner pods. They are also used to work the teleporter that Dr. Mossman helped build for the Combine. The command panels in the Citadel are only seen conveying Breencasts, while they most probably possess other functions as well.

Command panels can only be operated by Combine personnel. However, Alyx is seen using an EMP device to assume control of the panels. Barney has a limited Civil Protection clearance, which allows him to operate some, but not all of the panels.

Heavy doors

Heavy doors can be found anywhere in the Citadel or Nova Prospekt, and correspond with a command panel or a standard Combine lock, and can only be opened by the Combine. It is unknown what sort of mechanical device transports such a large piece of equipment, but it is known that Combine doors are generally guarding something important like an elevator or pod access points. Although the Combine doors can only be opened by soldiers, Alyx can open them with her EMP tool. Furthermore, heavy doors can activate alarms depending on their importance, like the Nova Prospekt thumpers.

Bunkers

Seen mostly lining the coast to Nova Prospekt, Combine bunkers house soldiers and supplies. Provided mainly for defense against antlions and other intruders, Combine bunkers are virtually bullet proof, with one to five mounted pulse guns, and a small entry/exit door at the rear of the building. Bunkers also house alarm switches. Some of the bunkers seen near Nova Prospekt can also be seen embedded with the rock face, and contain none of the liquid-like forcefields over the windows. Also seen here were two bunkers connected to make one.

Door lock

A Combine door lock is a small, metallic device that is placed on a door instead of a door handle, and acts to keep the door locked in order to prevent unauthorised access. Locks are most commonly found in the residential apartments throughout City 17. This could possibly be because the Combine, in its oppressive nature, chooses when the citizens are allowed to enter or leave their apartments, and monitor everyone that walks in and out. It is evident that only Combine personnel may operate a lock, but Alyx can use her EMP device to destroy Combine locks in order to gain access to restricted areas, like she does in Nova Prospekt.

Defensive structures

These range from portable fixed-gun emplacements that can be set up in a minute to full-sized barricades cordoning off entire streets. Instead of windows, they bear some sort of forcefield that resembles a liquid in appearance and offers ample protection against weapons. The doors that the barricades have are multi-sectioned and mounted on mechanical arms.

Watchtowers

Watchtowers are found throughout City 17, usually near defensive structures, and act to give Combine personnel a better view of the streets. There is usually a single Metro Cop on top of the watchtower, who may fire a flare once a reasonable force of Resistance is spotted, as a signal to call backup. Although most watchtowers are inaccessible by normal citizens, some Resistance members in the game climb up into them using ropes, and drop supply crates found up there down on the streets for the player. There are several variants of watchtowers located around City 17 and its boundaries. One of the most notable variants is the watchtower located on the surface inside the perimeter of Nova Prospekt which resembles a battle tower or small radio tower.

Forcefield generators

Scattered throughout City 17, the generators consist of two pylons, each one on either side of the path it is intended to protect. Invisible from a distance, the forcefield generated between the two pylons prevents entry of anything living that does not register with the system as being with the Combine, instead emitting a humming sound when in physical contact. However, other than vehicles drivable by the player, the system will not block inanimate objects. Some of them are seen in-game being powered off standard human power supply sockets, or from Combine APC batteries.

Thumpers

Used to protect cities from invasion by Antlions in the countryside, Thumpers are massive machines that repeatedly pound the ground using a set of metal beams. The vibrations they generate keeps Antlions away from the local area; they can be deactivated by anyone who can get close to them, however, by pressing the power button. The ones guarding Nova Prospekt are far larger than the standard ones, have spotlights, trigger the public warning system if deactivated, and of course have a larger range.

Generators

Combine Generators are mainly found within the Citadel, but can also be found in certain locations in City 17, such as the "Overwatch Nexus" or the plaza. The generators are used to power devices such as gates and locks, or weaponry-like the Suppression Device. There are a lot more generators in the Citadel than anywhere else, supplying power to systems in the immediate area such as forcefields.

In appearance, the generators look a lot like large cylinders, with a solid base and top and liquid sides, like those seen on defensive structures. The generator has a core with orbs floating within, which create a beam of something resembling electricity that runs from the top to the bottom of the generator. The orbs are the actual things that generate the power, as when they're knocked out (by the Gravity Gun, for instance), the generator will cease to function (however, if a free-moving orb is near enough to a module, the generator can actually draw it in to resume power generation). Generators powering critical systems typically have about three orbs inside them, but ones that power smaller devices will have just a single orb. There are special generators found only in the Citadel, which can have a limitless amount of orbs cycling through them, and seem to be orb transport paths of some sort.

Anyone unlucky enough to step into, or to be thrown inside a generator will be disintegrated, just as they would be if they got hit by an orb launched from a pulse rifle. The orbs launched from the pulse rifle appear to be identical to those in the generator, so it is likely that the Combine "package" such orbs into ammunition which can be launched by the pulse rifle.

In the Valve Hammer Editor, the protective field that keeps the power orbs inside the generators can be removed, allowing it to float freely through the room. By jumping directly on top of the orb, the user can actually bounce into the air. The faster the movement for the orb, the higher the user is bounced.

Mobile walls

Seen surrounding the Citadel and certain areas of Nova Prospekt, mobile walls are actually machines, using powerful drive systems in tandem with heavy metal blocks to slowly expand outward and destroy existing structures in the way. Standard operation is to lift and force a set of blocks outward, before allowing them to drop, and then alternating with another set.

Razor Trains

Large, mostly featureless and imposing. Aside from probably being custom-built to work on human rail networks transporting both standard and secret cargo and people, there is nothing particularly threatening about them. They don't seem to hold any visible crew, and are taller than standard locomotives and may be automated.

Ration dispenser

Seen only in the City 17 train station at the start of the storyline, window-mounted Combine ration dispensers serve to supply citizens with packaged food supply, given through a tray that slots out of the machine. More than often, citizens are required to wait in front of the machine for as long as minutes to receive their rations. Besides its fundamental function, little else is known about these devices. According to the citizens, the food is not good at all, as quoted by some citizens: "I'm ready to join Civil Protection just to get a decent meal," and "You gotta be damn hungry to wait in line for this crap."

Appearances in other media

The use of sandbox applications like Garry's Mod have allowed for Combine non-player characters to be used in a variety of webcomics and machinima productions. The Combine are also referenced in the Portal series.[3] In one webcomic, Concerned, the Combine are portrayed as a highly bureaucratic and often inept organization. One issue shows a Civil Protection briefing for attempting to capture the comic's protagonist Gordon Frohman, in which officers are instructed to cluster around explosive barrels, seek cover on unstable structures and rappel down from bridges in front of fast moving vehicles.[4] In another example, the machinima series Combine Nation follows Civil Protection officers in a similar style to police procedural documentaries. The officers perform their duties with various twists, such as the team's medical officer having an obsession with adhesive bandages and the legal consultant, an Overwatch soldier, favoring dramatic entries, such as throwing flashbangs, which often backfire on him.[5] Another web series, called The Combine, parodies the TV show The Office. This series attempts to portray the combine as an intergalactic corporation that suffers from everyday office issues and problems. One episode shows the soldiers attempting to bypass a webfilter so they can watch videos online instead of working.[6] Other media portray the Combine with more serious overtones, such as the live-action video The Combine Interview, which parodies an interview with Tom Cruise discussing Scientology. The video, described by ActionTrip as "eerie, to say the least"[7] and by both Joystiq[8] and Kotaku[9] as "creepy", instead presents an interview with a Civil Protection officer discussing the Combine's rule of Earth, adapting Cruise's words to fit the Combine theme. PC Gamer UK noted that "the suggestion, of course, is that Scientology's purpose or self-image in some way resembles that of the homogenising intergalactic murderous alien collective".[10]

↑Valve. Portal. (Valve). Level/area: "Test Chamber 19", final boss. (October 9, 2007) "GLaDOS: What's going on out there will make you wish you were back in here. I have an infinite capacity for knowledge, and even I'm not sure what's going on outside. All I know is I'm the only thing standing between us and them. Well, I was."